Bristol-Myers Squibb Co. (BMY - Get Report)   reported fourth-quarter results on Monday, Feb. 5 that topped analysts' estimates and said an ongoing clinical trial combining its Opdivo (nivolumab) and Yervoy (ipilimumab) drugs in lung cancer achieved one of its primary goals.

Shares of the giant drugmaker initially rose about 3% in pre-market trading after the results were released, but by morning trading, they were down 1.6% to $62.38.

Bristol-Myers said that in the Phase 3 study, dubbed CheckMate -227, the Opdivo-Yervoy combo showed "highly statistically significant" progression-free survival compared with chemotherapy in patients with advanced lung cancer and a high rate of tumor mutation. Progression-free survival refers to the period of time during and after treatment that a patient lives with the disease but it does not worsen. 

"We consider today's results as a breakthrough in cancer research, and we're excited for what this means for patients and for the treatment of lung cancer," said Bristol-Myers chairman and CEO Giovanni Caforio on an earnings call on Monday.

In a company news release, Matthew D. Hellmann, study investigator and medical oncologist at Memorial Sloan Kettering Cancer Center, said the clinical trial "showed that TMB is an important, independent predictive biomarker that can identify a population of first-line NSCLC patients who may benefit from the nivolumab plus ipilimumab combination."

Bristol-Myers also said that based on an interim analysis for overall survival, the Data Monitoring Committee recommended the continuation of the study. Overall survival refers to the period of time either from the diagnosis date or the beginning of treatment that a patient is still alive.

Bristol-Myers reported non-GAAP diluted earnings per share of 68 cents, up 8% from the same period in 2016. Revenue rose 4% to $5.45 billion.

Analysts expected, on average, adjusted EPS of 67 cents on revenue of $5.35 billion, according to Bloomberg.

For full-year 2018, Bristol-Myers expects non-GAAP EPS of $3.15 to $3.30.